1. Field of the Invention
This invention relates to a process for removing hydrogen sulfide from a waste water stream.
2. Description of Information Disclosures
Processes for removing volatilizable contaminants from a water stream by vacuum flashing are known.
U.S. Pat. No. 3,898,058 discloses removing hydrocarbons and other contaminants from a contaminated water stream by introducing a hot contaminated water stream into a contacting vessel and applying a vacuum to the vessel to separate the hydrocarbons and other contaminants from the waste water. It further discloses that when hydrogen sulfide is to be removed as a water contaminant or when the contaminant is carbon dioxide, the pH of the water is lowered to an acid condition prior to vacuum flashing.
U.S. Pat. No. 4,551,158 discloses removing hydrogen sulfide from a spent aqueous amine-containing absorbent without the use of a stripping column by flashing the spent absorbent in two or more flash stages in which a final stage is operated under reduced pressure of, for example, 0.5 to 1 bar.
When the hydrogen sulfide-containing water stream which is to be treated comprises a high concentration of alkali metal components, such as salts, treatment of such water poses addition problems to avoid equipment plugging due to salt deposition.
It has now been found that salt deposition can be minimized and the desired level of hydrogen sulfide removal achieved by controlling the pH and the temperature of the hydrogen sulfide-containing water stream within specified ranges.